In the Heart of the Sea is a terrific special effects movie and a great atmospheric, period adventure. But it does drag near the end of the second act, and there isn’t as much drama among the men as there could have been. They get along remarkably well for a disparate group of individuals who have to brave the dangers of the sea together on a voyage that lasts roughly a year and a half.

Before oil, it was whale oil that fueled lamps everywhere, and the demand for it was great. If you read Herman Melville’s Moby-Dick and didn’t skip over the cetology chapters, you know that whaling ships were floating factories that not only pursued whales, but also processed them right there on the spot.

It’s one thing to read about it, but director Ron Howard creates a film that graphically shows the process, from the harpooning of a female while her calf swims next to her to the eventual killing and processing—which at one point requires the smallest sailor onboard to crawl inside the fetid whale to make sure every bit of it is harvested before the sharks come to take the rest. It’s fascinatingly realistic, but if you’re an animal lover it can be painful to watch.

In the Heart of the Sea is rated PG-13, and it’s the kind of film that could traumatize youngsters if they see it before they’re able to handle it—and not just because of the whale harvest, or the violence that ensues when a rogue white whale seems to understand what the whalers are doing and tries to destroy them. This film is based on the book In the Heart of the Sea: The Tragedy of the Whaleship Essex by Nathaniel Philbrick, and it doesn’t just tell the story of an 1820 incident that became the basis for Melville’s famous novel. It’s what happens after the whale cripples the Essex that will leave a permanent impression on young viewers. You can probably guess the spoiler I won’t share, but when the frame for the story involves Herman Melville visiting the remaining survivor of the Essex and trying to get him to tell his story of survival, if it’s something so unspeakable that the man kept it secret for all his adult life, well, that’s the kind of thing that will leave an impression on children. So the PG-13 rating is mostly because of “thematic material.”

Moby-Dick was all about Capt. Ahab’s obsession with capturing a white whale, and there’s none of that here, and nothing that comes even close to the tension that came between Ahab and his whalers. There are no tattooed harpooners here and nobody builds a coffin—though there is a character named Coffin. While there isn’t a specific point of view, we mostly see things as they affect veteran first mate Owen Chase (Chris Hemsworth), who is justifiably angered when the fleet owners renege on their promise to make him captain and instead assign him to be first mate again to a rookie whose family is prominent in the whaling business.

Curiously, there’s not nearly the conflict between Capt. George Pollard (Benjamin Walker) and Chase as you might expect. Even the men get along fairly well, partly because Charles Leavitt’s screenplay focuses on the man-versus-nature main plot and all but ignores side plots involving conflicting personalities. But when the film drags at one point you find yourself wishing he had developed minor conflicts. As is, In the Heart of the Sea is a straightforward sea adventure, and the device of leaving the action to return to Melville and survivor Thomas Nickerson (Tom Holland) isn’t as successful as the filmmakers think it is. Some of the dialogue in those scenes gets a bit syrupy, hokey, cheesy—pick an adjective—and you get the feeling much more could have been done to explore the attitudes of the young and old Nickersons. Those are my complaints, but give Howard credit for creating some of the most realistic whaling scenes ever to be shown on the big screen. The characters may seem shallow as pawns in an existential chess match, but the action is something else.

Language: Not much, really, besides a few damns and hellsSex: n/a (unless you count a scrimshaw drawing of a topless woman)Violence: Harpooning and whale violence against the shipsAdult situations: Atrocities committed while surviving adrift. (SPOILER: we’re talking Donner Party)Takeaways: Moby-Dick may be the more compelling story, but this tale of the incident that inspired it is still pretty darned good as a period adventure.